Perovskite type high-temperature thermoelectric ceramic material and preparation method thereof

Abstract

The invention relates to a perovskite type high-temperature thermoelectric ceramic material, which is a thermoelectric ceramic material Sr (1-x) Sm (x) Ti (1-y) TayO3 formed by co-doping metal elements of samarium and tantalum by taking strontium titanate as a matrix, x is equal to 0.05-0.12, and y is equal to 0.01-0.03. Sm and Ta with specific amounts are co-doped in strontium titanate, so that the Seebeck coefficient (about 1300K) of the perovskite ceramic material is effectively improved from 278.66 [mu] V / K of single doped Sm to 663.61 [mu] V / K), the heat conductivity (about 1300K) of the perovskite ceramic material is reduced from 278.66 [mu] V / K of single doped Sm to 663.61 [mu] V / K), and meanwhile, the conductivity of the material is not reduced, so that the thermoelectric figure of merit of the ceramic is improved to 1.3, and the thermoelectric figure of merit of the perovskite ceramic material is greatly improved. The Sm-doped strontium titanate ceramic material is three times that of a single Sm-doped strontium titanate ceramic material.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric material preparation, and particularly relates to a perovskite-type high-temperature thermoelectric ceramic material and a preparation method thereof. Background Art

[0002] Thermoelectric materials are functional materials that can directly convert thermal energy and electrical energy into each other. Thermoelectric materials have a thermoelectric effect. When one end of a thermoelectric material is heated, the electrons at the heated end have a higher temperature, and the heated electrons will move to the end with a lower temperature. During this movement, an electric current will be generated, and charge accumulation will occur at both ends of the material. The charge accumulation will cause a potential difference to form at both ends. Based on the thermoelectric effect, we can prepare thermoelectric refrigeration and thermoelectric power generation devices.

[0003] The performance of thermoelectric materials is evaluated by the dimensionless thermoelectric figure of merit ZT. For thermoelectric materials, whether used for power generation or refrigeration, it is desired that the ZT value of the thermoelectric material is as high as possible. Its calculation formula is as follows:

[0004] Among them, K is the thermal conductivity, σ is the electrical conductivity, S is the thermoelectric potential, and T is the absolute temperature. It can be seen from the formula that for a good thermoelectric material, both its Seebeck coefficient and electrical conductivity should be large, while its thermal conductivity should be kept small. In practical applications, for a material with a thermoelectric figure of merit ZT close to 1, its efficiency reaches the commercial application level and it is possible to be widely used.

[0005] The currently discovered thermoelectric materials mainly include metal alloy thermoelectric materials, oxide thermoelectric materials, and composite thermoelectric materials, etc. Alloy materials have high thermoelectric conversion efficiency and good effects under low-temperature and room-temperature conditions, but in high-temperature environments, the materials are prone to oxidation and unstable performance. Oxide thermoelectric materials have stable performance at various environmental temperatures, simple preparation processes, and long service lives. Perovskite-type oxide thermoelectric materials belong to a type of oxide thermoelectric materials. Although strontium titanate thermoelectric materials have a relatively high Seebeck coefficient, their thermal conductivity is also high, and their bandgap is large and their electrical conductivity is low. This has a great impact on the thermoelectric figure of merit, making it not a high-quality thermoelectric material in itself. Therefore, element doping is required to improve the thermoelectric performance and applicable temperature of the material. The research on doping modification of strontium titanate is of great significance for the development of environmentally friendly thermoelectric materials. The prior art ("Improvements in the thermoelectric efficiency of SrTiO 3through donor doping” Hamed Bakhshi et al., 《Ceramics International》) has co-doped strontium titanate with metallic samarium and niobium. However, after doping Sm on the basis of Nb, the Seebeck coefficient of the ceramic material has decreased significantly. Finally, the highest thermoelectric figure of merit of the material is only 0.4 at 850K. There is also (”Synthesis and thermoelectric performance of Ta doped Sr 0.9 La 0.1 TiO 3 ceramics” H.C. Wang et al.,) which has co-doped strontium titanate with lanthanum and tantalum. By adjusting the doping amount of tantalum on the basis of lanthanum, it is found that as the amount of tantalum increases, the Seebeck coefficient also decreases, and finally the thermoelectric figure of merit also decreases. The thermoelectric figure of merit of the finally prepared strontium titanate-based ceramic materials is not ideal, and it is extremely difficult to exceed 1.0. Summary of the Invention

[0006] In order to solve the above problems, the object of the present invention is to provide a perovskite-type high-temperature thermoelectric ceramic material, which effectively improves the Seebeck coefficient of the strontium titanate-based ceramic material in a high-temperature environment, significantly reduces the thermal conductivity at the same time, and does not increase the electrical conductivity, thereby effectively improving the thermoelectric figure of merit of the material.

[0007] Another object of the present invention is to provide a preparation method of the above perovskite-type high-temperature thermoelectric ceramic material.

[0008] The object of the present invention is achieved by the following technical solutions: A perovskite-type high-temperature thermoelectric ceramic material, characterized in that: it is a thermoelectric ceramic material Sr formed by using strontium titanate as the matrix and co-doping with metallic elements samarium and tantalum 1-x Sm x Ti 1-y Ta y O 3 , where x = 0.05~0.12, y = 0.01~0.03.

[0009] Preferably, in the thermoelectric ceramic material, Sr 0.92 Sm 0.08 Ti 1-y Ta y O 3 , y = 0.01~0.03.

[0010] Further preferably, in the thermoelectric ceramic material, Sr 0.92 Sm 0.08 Ti 1-y Ta y O 3In it, y = 0.02, that is, the thermoelectric ceramic material is Sr 0.92 Sm 0.08 Ti 0.98 Ta 0.02 O 3 .

[0011] A preparation method of a perovskite high-temperature thermoelectric ceramic material, characterized in that: zirconium balls, raw materials and ethanol are ball-milled once, and then dried to obtain a mixture, the mixture is pre-sintered to obtain a pre-synthesized powder, then ball-milled for the second time, and finally plasma-sintered into a ceramic.

[0012] Furthermore, in the first ball-milling, the zirconium balls, raw materials and ethanol are mixed at a mass ratio of 1:1:1, ball-milled at 400-600 rpm for 10-14 h, and after the ball-milling is completed, dried at 70-90 °C to obtain a mixture.

[0013] Furthermore, the raw materials are strontium carbonate (SrCO 1-x Sm x Ti 1-y Ta y O 3 ), samarium oxide (Sm 3 ), titanium dioxide (TiO 2 O 3 ), and tantalum oxide (Ta 2 O 2 O 5 ) calculated according to the molar ratio of the corresponding elements in Sr

[0014] Furthermore, the pre-sintering is to keep the dried mixture at 1150-1250 °C for 3-5 h, and then naturally cool it to room temperature to obtain a pre-synthesized powder.

[0015] Furthermore, in the second ball-milling, the pre-synthesized powder is mixed with an equal amount of zirconium balls and ethanol, ball-milled at 400-600 rpm for 10-14 h, and ground after drying to obtain a second ball-milled powder.

[0016] Furthermore, in the plasma sintering, the ground powder is heated to 1110-1150 o °C within 8-12 min, kept warm for 4-6 min, and the sintering pressure is 45-55 Mpa to sinter into a ceramic material.

[0017] In the present invention, strontium titanate is co-doped with samarium and tantalum elements, which causes vacancies. By adjusting the oxygen vacancy concentration, the Seebeck coefficient is increased, the thermal conductivity of the material is reduced while the conductivity is not reduced to obtain a high thermoelectric figure of merit. Due to the differences in the atomic radii of the doped elements, the crystal structure changes to varying degrees, and the lattice vibration also changes accordingly, affecting the lattice wave, reducing the scattering it receives and increasing the thermal conductivity.

[0018] Most specifically, a preparation method of a perovskite high-temperature thermoelectric ceramic material is characterized by comprising the following steps (1) Using strontium carbonate (SrCO 3 ), samarium oxide (Sm 2 O 3 ), titanium dioxide (TiO 2 ), and tantalum oxide (Ta 2 O 5 ), the raw materials are composed according to the molar ratio of elements Sr, Sm, Ti, and Ta of 0.88~0.95:0.05~0.12:0.97~0.99:0.01~0.03. Zirconium balls, raw materials, and ethanol are mixed in a mass ratio of 1:1:1 and placed in a ball mill, ball-milled at 400~600 rpm for 10~14 h, and then discharged and dried at 70~90 °C to obtain a mixture; (2) Keeping the mixture prepared in step (1) at 1150~1250 °C for 3~5 h, and then naturally cooling to room temperature to obtain a pre-synthesized powder; (3) Mixing the pre-synthesized powder, zirconium balls, and ethanol in a mass ratio of 1:1:1, ball-milling at 400~600 rpm for 10~14 h, then discharging and drying at 70~90 °C, and grinding to obtain a secondary ball-milled powder; (4) Loading the secondary ball-milled powder into a graphite mold with a diameter of 15 mm, placing it in a spark plasma sintering furnace, heating to 1110~1150 o °C within 8~12 min, keeping warm for 4~6 min, and the sintering pressure is 45~55 Mpa to sinter into a ceramic material.

[0019] The present invention has the following technical effects: By co-doping specific amounts of Sm and Ta in strontium titanate, the present invention reduces the sintering temperature during the preparation process, effectively increases the Seebeck coefficient of the perovskite ceramic material (from 278.66 μV / K of single-doped Sm to 663.61 μV / K at about 1300 K), reduces its thermal conductivity (from 278.66 μV / K of single-doped Sm to 663.61 μV / K at 1300 K), and does not reduce the conductivity of the material, thereby increasing the thermoelectric figure of merit of the ceramic to 1.3, which is 3 times that of the strontium titanate ceramic material with single-doped Sm. Description of the Drawings

[0020] Figure 1 : Sr prepared at 1130 °C 0.92 Sm 0.08 Ti 1-y Ta y O 3 SEM images of the cross-section of the sample; (a) y = 0, (b) y = 0.01, (c) y = 0.02, (d) y = 0.03.

[0021] Figure 2 : Sr prepared in Example 1 0.92 Sm 0.08 Ti 1-y Ta y O 3 XRD pattern.

[0022] Figure 3 : Sr prepared in Example 1 0.92 Sm 0.08 Ti 1-y Ta y O 3 Resistivity variation curve with temperature.

[0023] Figure 4 : Sr prepared in Example 1 0.92 Sm 0.08 Ti 1-y Ta y O 3 Seebeck coefficient variation with temperature.

[0024] Figure 5 : Sr prepared in Example 1 0.92 Sm 0.08 Ti 1-y Ta y O 3 Thermal diffusivity variation with temperature.

[0025] Figure 6 : Sr prepared in Example 1 0.92 Sm 0.08 Ti 1-y Ta y O 3 Thermal conductivity variation with temperature.

[0026] Figure 7 : Sr prepared in Example 1 0.92 Sm 0.08 Ti 1-y Ta y O 3 Power factor variation with temperature.

[0027] Figure 8: Sr prepared in Example 1 0.92 Sm 0.08 Ti 1-y Ta y O 3 The thermoelectric figure of merit varies with temperature.

[0028] Figure 9 : Sr prepared in Example 1 0.92 Sm 0.08 Ti 1-y Ta y O 3 The bandgap width changes. DETAILED DESCRIPTION

[0029] The present invention is described in detail below through examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above-mentioned contents of the present invention.

[0030] Comparative Example 1: (1) Sr doped with Sm alone 1-x Sm x TiO 3 Preparation: The preparation steps are the same as those in Example 1, except that the raw materials do not contain Ta. 2 O 5 , respectively adjust Sm 2 O 3 The doping amount, i.e. x=0.05, 0.08, 0.10, 0.12, during the sintering process, the ceramic structure that cannot be effectively sintered at 1110~1150℃ is not ideal, and the sintering temperature needs to be further increased to above 1400℃.

[0031] Prepared Sr with different Sm doping amounts 1-x Sm x TiO 3 The Seebeck coefficients of Sm-doped strontium titanate vary between -100 and -250 μV / K, and the Seebeck coefficient decreases with increasing doping levels. The thermoelectric performance of Sm-doped strontium titanate increases with increasing temperature to 800 K, with Sr 0.9 Sm 0.1 TiO 3 The thermoelectric figure of merit is the highest, which is only 0.22 at 800K.

[0032] (2) SrTi doped with Ta alone 1-y Ta y O 3 Preparation: Each preparation step is the same as that in Example 1 above, except that the raw materials do not contain Sm. 2 O 3 , and the doping amounts of Ta 2 O 5 are adjusted respectively, that is, y = 0.01, 0.03, and 0.05. During the sintering process, ceramics with a good structure cannot be effectively sintered at 1110 - 1150 °C, and the sintering temperature needs to be further increased to above 1400 °C.

[0033] The Seebeck coefficients of the prepared SrTi 1-y Ta y O 3 with different Ta dopings vary between -100 and -250 μV / K, and the Seebeck coefficient shows a downward trend with the increase of Ta doping amount. With the increase of Ta doping amount, the thermoelectric figure of merit shows a gradually decreasing trend.

[0034] Example 1 A preparation method of a perovskite high-temperature thermoelectric ceramic material Sr 1-x Sm x Ti 1-y Ta y O 3 includes the following steps: (1) Using strontium carbonate (SrCO 3 ), samarium oxide (Sm 2 O 3 ), titanium dioxide (TiO 2 ), and tantalum oxide (Ta 2 O 5 ) to form raw materials according to the molar ratio of elements Sr, Sm, Ti, and Ta of 0.92:0.08:0.98:0.02. Mix zirconium balls, raw materials, and ethanol in a mass ratio of 1:1:1, place them in a ball mill, ball mill at 500 rpm for 12 h, and then discharge and dry at 80 °C to obtain a mixture; (2) Keep the mixture prepared in step (1) at 1200 °C for 4 h, and then naturally cool to room temperature to obtain a pre-synthesized powder; (3) Mix the pre-synthesized powder, zirconium balls, and ethanol in a mass ratio of 1:1:1, ball mill at 500 rpm for 12 h, then discharge and dry at 80 °C, and grind to obtain a secondary ball-milled powder; (4) Load the secondary ball-milled powder into a graphite mold with a diameter of 15 mm, put it into a spark plasma sintering furnace, heat up to 1130 o °C in 10 min, keep it warm for 5 min, and the sintering pressure is 50 Mpa to sinter into a ceramic material Sr 0.92 Sm 0.08 Ti 0.99 Ta0.01 O 3 (denoted as Sm08Ta01-STO).

[0035] According to the above steps, by changing the content of Ta in the raw materials and adjusting the doping amount of Ta, Sr 2 O 5 was respectively prepared by adjusting the doping amount of Ta, and Sr 0.92 Sm 0.08 TiO 3 (denoted as Sm08-STO), Sr 0.92 Sm 0.08 Ti 0.98 Ta 0.02 O 3 (denoted as Sm08Ta02-STO) and Sr 0.92 Sm 0.08 Ti 0.97 Ta 0.03 O 3 (denoted as Sm08Ta03-STO).

[0036] The SEM image of the cross-section of the Sr 1-x Sm x Ti 1-y Ta y O 3 prepared in this example is shown as follows. By observation, it can be found that with the increase of tantalum content, the grains tend to increase. Due to the fast sintering speed of spark plasma sintering, the grain size is 100 - 200 nm, and the fracture surface is mainly intergranular fracture after Ta doping. Figure 1

[0037] Figure 2 Figure 0.92 Sm 0.08 Ti 1-y Ta y O 3 is the X-ray diffraction pattern of Sr samples with different Ta doping concentrations. According to the diffraction peaks in the figure, the standard powder diffraction card (PDF#35-0734) of samarium and tantalum doped strontium titanate powder samples and strontium titanate is compared. It can be obtained that the positions, peak shapes and peak widths of the diffraction peaks of the samples are basically consistent with those of the strontium titanate material diffraction peaks. From this, it can be known that the crystal structure of the samarium and tantalum doped strontium titanate powder samples is still the perovskite structure, and no crystal structure change has occurred. The positions of the diffraction peaks of the powders with different concentrations have a slight shift, indicating that different doping concentrations cause different degrees of lattice distortion of strontium titanate. The change in the width of the peaks indicates that the grain size changes to a certain extent with the doping of samarium and tantalum elements.

[0038] Figure 3 Figure 0.92 Sm 0.08 Ti 1-y Ta​y O 3 The resistivity change curve of the sample with temperature. It can be seen that in the lower temperature range (0 - 800 °C), at the same temperature, as the doping amount of Ta increases, the resistivity of the sample shows an upward trend. While in the higher temperature range (above 1000 °C), the co - doping of Ta and Sm has basically no effect on the resistivity of the sample.

[0039] Figure 4 is Sr 0.92 Sm 0.08 Ti 1-y Ta y O 3 The Seebeck coefficient change curve of the sample with temperature. It can be seen that the Seebeck coefficient of the sample is negative, indicating that the SrTiO₃ ceramic co - doped with Sm and Ta is an n - type semiconductor. Among them, the Seebeck coefficient of the Sm08 - STO sample increases with the increase of the sintering temperature, with a minimum value of 110.11 μV / K at 300 K and reaching a maximum of 278.66 μV / K at 1000 °C. After further doping with Ta, the Seebeck coefficient changes significantly. Generally speaking, with the further doping of Ta, at the same temperature, the Seebeck coefficient shows an obvious increasing trend compared with that without Ta doping, and the highest is Sr 0.92 Sm 0.08 Ti 0.97 Ta 0.03 O 3 sample, reaching 663.61 μV / K at 1000 °C, which is 2.38 times that of the Sr 0.92 Sm 0.08 TiO 3 When doping with a single Ta, as the doping amount of Ta increases, the Seebeck coefficient shows a downward trend at the same temperature. It can be seen that the doping of samarium and tantalum greatly improves the thermoelectric performance of strontium titanate, and the most suitable temperature for its application is in the high - temperature region.

[0040] Figure 5 and Figure 6 are Sr 0.92 Sm 0.08 Ti 1-y Ta y O 3 The curves of the thermal diffusivity and thermal conductivity of the SrSmTiTaO sample with temperature. The thermal conductivity is calculated based on the thermal diffusivity. It can be seen that both show a downward trend with the increase of temperature. A good thermoelectric material requires a lower thermal conductivity. It can be seen that the increase in the content of samarium and tantalum causes an increase in the thermal conductivity, but the overall trend indicates that the strontium titanate material is suitable for high - temperature environments.

[0041] Figure 7 and Figure 8 are Sr 0.92Sm 0.08 Ti 1-y Ta y O 3 Curves of the power factor and thermoelectric figure of merit of the sample varying with temperature. These two values are characteristic quantities describing the comprehensive thermoelectric performance of the material, calculated by combining the Seebeck coefficient, electrical conductivity, thermal conductivity and other values measured previously. The higher the values of both, the better. As can be seen from the figure, with the increase of temperature, both the power factor and the thermoelectric figure of merit are increasing, indicating that the thermoelectric performance of samarium- and tantalum-codoped strontium titanate ceramic materials has been improved, and the performance is the best at 1000 °C. Among them, the thermoelectric figure of merit of Sm08Ta03-STO reaches 1.3.

[0042] After preparing Sr by plasma sintering 0.92 Sm 0.08 Ti 1-y Ta y O 3 For the sample, it can be found that when the sintering temperature is from 1110 °C to 1150 °C, by observing the microstructure of the sample, it is found that at the sintering temperature of 1150 °C, most of the grains have blurred boundaries, because the co-doping of samarium and tantalum elements reduces the sintering temperature of strontium titanate materials.

[0043] Since the band gap of strontium titanate material is relatively wide, it can be classified as a wide-bandgap insulator with extremely poor electrical conductivity. As Figure 9 shown, the introduction of samarium and tantalum elements also reduces the band gap of Sr 0.92 Sm 0.08 Ti 1-y Ta y O 3 sample, improving the previous defect of large band gap resulting in low electrical conductivity.

[0044] Example 2 A preparation method of a perovskite high-temperature thermoelectric ceramic material, comprising the following steps: (1) Using SrCO 3 , Sm 2 O 3 , TiO 2 and Ta 2 O 5 to form raw materials according to the molar ratio of elements Sr, Sm, Ti and Ta of 0.88:0.12:0.98:0.02. Mix zirconia balls, raw materials and ethanol in a mass ratio of 1:1:1, place them in a ball mill, ball mill at 400 rpm for 14 h, and then discharge and dry at 70 °C to obtain a mixture; (2) Keep the mixture prepared in step (1) at 1150 °C for 5 h, and then naturally cool to room temperature to obtain a pre-synthesized powder; (3) Mix the pre-synthesized powder, zirconium balls, and ethanol in a mass ratio of 1:1:1, ball mill at 600 rpm for 10 h, then discharge and dry at 90 °C, and grind to obtain the secondary ball-milled powder; (4) Load the secondary ball-milled powder into a graphite mold with a diameter of 15 mm, place it in a spark plasma sintering furnace, heat up to 1110 o °C in 8 min, hold for 6 min, and the sintering pressure is 55 Mpa to sinter into a ceramic material.

[0045] The Sr 0.88 Sm 0.12 Ti 0.98 Ta 0.02 O 3 prepared in this example has a thermoelectric figure of merit of 1.0 at 1000 °C.

[0046] Example 3 A preparation method of a perovskite high-temperature thermoelectric ceramic material, comprising the following steps: (1) Using SrCO 3 , Sm 2 O 3 , TiO 2 and Ta 2 O 5 to form raw materials according to the molar ratio of elements Sr, Sm, Ti, and Ta of 0.95:0.05:0.98:0.02. Mix the zirconium balls, raw materials, and ethanol in a mass ratio of 1:1:1 and place them in a ball mill, ball mill at 600 rpm for 10 h, then discharge and dry at 90 °C to obtain a mixture; (2) Keep the mixture prepared in step (1) at 1250 °C for 3 h, then naturally cool to room temperature to obtain the pre-synthesized powder; (3) Mix the pre-synthesized powder, zirconium balls, and ethanol in a mass ratio of 1:1:1, ball mill at 400 rpm for 14 h, then discharge and dry at 70 °C, and grind to obtain the secondary ball-milled powder; (4) Load the secondary ball-milled powder into a graphite mold with a diameter of 15 mm, place it in a spark plasma sintering furnace, heat up to 1150 o °C in 12 min, hold for 4 min, and the sintering pressure is 45 Mpa to sinter into a ceramic material.

[0047] The Sr 0.95 Sm 0.05 Ti 0.98 Ta 0.02 O 3 prepared in this example has a thermoelectric figure of merit of 1.1 at 1000 °C.

Claims

1. A perovskite-type high-temperature thermoelectric ceramic material, characterized in that: Thermoelectric ceramic material Sr is based on strontium titanate and co-doped with metal elements samarium and tantalum. 1-x Sm x Ti 1-y Ta y O3, where x=0.05~0.12, y=0.01~0.

03.

2. A method for preparing the perovskite high temperature thermoelectric ceramic material according to claim 1, characterized in that: The zirconium balls, raw materials and ethanol are ball-milled once, and then dried to obtain a mixture, the mixture is pre-sintered to obtain a pre-synthesized powder, and then ball-milled twice, and finally plasma sintered to obtain ceramics.

3. The method for preparing a perovskite high temperature thermoelectric ceramic material according to claim 2, characterized in that: The first ball milling is to mix the zirconium balls, the raw materials and the ethanol in a mass ratio of 1:1:1, and ball mill for 10-14 h at 400-600 rpm. After the ball milling, the mixture is dried at 70-90° C. to obtain the mixture.

4. A method for preparing a perovskite high-temperature thermoelectric ceramic material according to claim 2 or 3, characterized in that: The raw materials are composed of strontium carbonate (SrCO3), samarium oxide (Sm2O3), titanium dioxide (TiO2) and tantalum oxide (Ta2O5) according to the molar ratio of elements Sr, Sm, Ti and Ta of 0.88~0.95:0.05~0.12:0.97~0.99:0.01~0.

03.

5. A method for preparing a perovskite high temperature thermoelectric ceramic material according to any one of claims 2 to 4, characterized in that: The pre-calcination is to keep the dried mixture at 1150-1250° C. for 3-5 hours, and then naturally cool it to room temperature to obtain pre-synthesized powder.

6. A method for preparing a perovskite high temperature thermoelectric ceramic material according to any one of claims 2 to 5, characterized in that: The secondary ball milling is to mix the pre-synthesized powder with an equal amount of zirconium balls and ethanol, ball mill at 400-600 rpm for 10-14 hours, dry and grind to obtain the secondary ball milled powder.

7. The method for preparing a perovskite high temperature thermoelectric ceramic material according to claim 6, characterized in that: The plasma sintering is to heat the ground powder to 1110~1150 in 8~12 minutes. o C, keep warm for 4~6min, sintering pressure is 45~55Mpa, and sintering into ceramic material.

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